This invention is suitable for use systems and machines for the industrial dyeing of reels of yarn and/or textile fibre wound on packages. For the sake of brevity, the term reel of yarn shall hereinafter always refer to a generic textile material that can include the various textile materials as set out above.
As is known, traditional machines for the dyeing of traditional reels of yarn, operate with the material fully or partially immersed in the dye bath.
Circulation of the dye bath through the material is such as to allow the best possible distribution of the dyeing fluid on the yarn being dyed.
The machine is also equipped with dyeing fluid recirculation means to forcibly induce the latter into transit according to a closed route that always involves passing through the reels of yarn being dyed. The direction of the dyeing fluid through the reels of yarn can also be inverted in accordance with standard timeframes and methods.
As described and illustrated in the MI2004A002124 document filed by the same Applicant, the recirculation means can also be equipped recirculation mechanism that is operatively placed within the machine chamber to ensure continuous movement of the dye bath. Although machines for the dyeing of reels of yarn are capable of high-quality dyeing, the Applicant has found that they are nevertheless not free of drawbacks and can be improved in various aspects, primarily in relation to the significant flow rate of the dyeing fluid when in movement, the high differential pressures that the circulation pump must generate to guarantee the required flow rate, the high level of electricity required, the uniformity of the concentration of colour on the yarn, the adjustment and uniformity of the temperature of the dye bath and the presence of deviation devices that reduce the overall performance of the pumps.
In particular, the Applicant has found that circulation within the dye bath must have an substantially high flow rate.
Homogeneity of dye bath temperature and the concentration of colour on all parts of the yarns being dyed is normally guaranteed via the execution of a high number of dye bath refills per minute, such as two to four bath refills per minute.
So as to ensure optimal colouring of the material, the circulation pumps must generate a significant differential pressure, of between 0.5 bar and 1.5 bar and high flow rates, for example.
Naturally, if the material being dyed has material characteristics that result in its preventing the dyeing fluid from forcibly passing through it, such as polyester or cotton for example, a circulation pump with a fairly high level of power must be used. In the case of more delicate materials, such as cashmere, fibres in top form and silk for example, the circulation flow rate of the dyeing fluid must be restricted. In this event, the input power is reduced in proportion to the reduction in the number of dye bath refills per minute.
In order to reduce the power requirements for the passing of dyeing fluid through the material to be dyed, without excessively compromising machine productivity, it has been proposed that the dyeing fluid not be supplied to all the reel-holders rods in the bath at the same time, but that it be supplied selectively and sequentially to a small part of the total number or said reel-holder rods.
This technology is illustrated in documents FR2429283 and U.S. Pat. No. 3,751,223 for example. The reel-holder rods are subdivided in groups and each group's supply is connected to a separate collector chamber. The circulation pump collects liquid from the container to sequentially transmit it to each collector chamber at an adequate pressure.
Tests conducted by the Applicant have shown a drawback of this technology that is perfectly justified from examination of its fluid-dynamic characteristics. Pump capacity is decreased to only a fraction of the capacity that would be required to simultaneously supply all the reels, with the same unit capacity in terms of passing through the material to be dyed, which is also imposed by its intrinsic characteristics. This reduction in the capacity of the circulating liquid leads to particularly poor circulation and movement of the liquid in which the reels are immersed.
This necessarily results in non-uniformity of distribution of both the concentration of dye in the bath in which the product to be dyed is immersed and the temperature of the liquid itself. Both these parameters result in the transfer of the colouring substance dispersed in the product so that the resulting unacceptable non-uniformity of dyeing of the product, achieved using machines of the type described in the prior documents as referred to above, is justified. This drawback appears to justify that there are no dyeing systems of this type currently in use or on the market, many years subsequent to the relevant theoretical proposal.
Surprisingly, the Applicant has now found that this drawback of the prior art has been overcome via the simple combining of the selective and sequential supply of liquid with a reasonable number of groups of reels with the adoption of means suitable for inducing recirculation or mixing of the liquid within the bath to the extent that it substantially maintains unaltered the characteristics of the liquid, in terms of the temperature and the concentration of the dyeing substance that it contains.
The completely satisfactory result achieved in terms of the dyeing uniformity with a machine according to the invention is not fully justifiable, as shown by the Applicant's tests. It could have been envisaged that a sufficiently powered recirculation of the dyeing fluid within the bath to maintain its concentration and temperature characteristics could have some advantageous effects, both in terms of the uniformity of exposure to the dye of the reels that the dyeing fluid is momentarily not passing through, and in that the characteristics of the liquid that the circulation pump collects from a certain point of the container, to then channel within the reels of material to be dyed, do not result modified by localised.
However, in tests, the combination of the sequential supply of groups of reels in a bath maintained in energetic circulation, resulted in unexpected qualitative results that are not inferior or are indeed superior to the results achieved by traditional machines, where the liquid is supplied to all the reels at the same time and passes through all the material to be dyed at the same time with an energy input that is many times in excess of the requirements of the machine according to the invention.